This invention relates to concrete pumps, and, more particularly, to a concrete pump with a hopper and a pivotable S-tube valve assembly.
Concrete pumps are well known in the construction industry and are used for pumping concrete or other pumpable construction materials. Concrete pumps are described, for example, in U.S. Pat. Nos. 3,612,730, 3,897,180, 4,241,641, and 6,305,916.
Most concrete pumps which are currently being manufactured include two concrete pumping cylinders and an S-shaped tube valve for alternately connecting the outlet end of each pumping cylinder to the discharge conduit of the concrete pump. The S-tube valve is pivotably mounted in a concrete hopper. As the piston in one of the pumping cylinders moves toward the hopper to pump concrete through the S-tube valve to the discharge conduit, the piston in the other pumping cylinder retracts away from the hopper to draw concrete into the cylinder.
A typical S-tube valve assembly is described in U.S. Pat. No. 6,305,916. The valve assembly includes an S-tube and a mounting plate for the S-tube which is pivotally mounted on the hopper. A wear ring is mounted in an opening in the valve assembly and engages a wear plate on the hopper.
U.S. Reissue Pat. No. 32,657 describes an S-tube valve with a flexible and resilient spring which is positioned in recesses in the S-tube and in the wear ring for forcing the wear ring against the wear plate. However, a portion of the S-tube which retains the spring is exposed to the abrasive action of the concrete which is pumped through the wear ring and the S-tube. That portion of the S-tube is therefore subject to wear, and when that portion is worn sufficiently so that the spring is no longer properly supported, the S-tube must be replaced.
A removable retainer ring is positioned between the spring and the S-tube valve assembly. The retainer ring abuts a face on the valve assembly and protects the face from abrasion. When the retainer ring wears out, the retainer ring can be replaced without replacing the valve assembly.